On the convective mass transfer and flow across spherical droplet falling in Casson fluids

Abstract

In this work, we have investigated the flow and mass transfer across spherical droplet falling in the non-Newtonian fluids (Casson fluids). For the different values of dimensionless parameters like Reynolds number; 1≤Re≤100 Bingham number; 0≤Bn≤ 50, viscosity ratio; 0.1≤κ≤10, and Schmidt number; Sc = 10. The governing equation of momentum and mass transport is solved numerically with Casson constitutive equation and appropriate boundary conditions. To prevent singularity in the Casson model, the Papanastasiou regularization model is introduced. Local transport properties are shown by streamlines and concentration contours, and average transport parameters, such as the Sherwood number, are presented over the surface of the droplet. Yielded and un- yielded zone were observed to coexist inside the flow domain due to the fluid-yield stress. The convective mass transfer was observed in the yielded fluid region while the un-yielded area is dominated by molecular diffusion. Furthermore, as value of Bingham number increases, the un-yielded area dominates, and yielded areas progressively disappear.